Patterned finishes on coated films are known and can be provided via the interaction between a carrier layer or substrate and a material disposed on the substrate (e.g., a coatable material), the patterned finish being formed upon removal of the carrier layer. Drying techniques have been employed to create a patterned finish using a roll having a heated surface that includes a pattern of discontinuities which, when contacting a coatable material such as a curable resin or the like, create a pattern within the surface of the material while drying it at the same time. The resulting article retains the pattern from the roller and the coatable material is left partially or fully dried, hardened and/or cured.
Embossing imparts a texture to a film using a patterned roller and is used most often in applications in which the durability of the film is not a concern. Embossing is not normally used in and does not address the need for matte hard coats for protective display applications, for example. Patterned films have also been made by first coating a flowable and coatable material (e.g., a resin) onto the patterned surface of a tool, the pattern being provided as cavities that receive the coatable material so that, once hardened or partially cured, a durable patterned film is provided. However, the creation and maintenance of patterned tooling is difficult and expensive.
Films with matte finishes have been created by the addition of beads or particles to a coatable material such as a resin or a polymeric precursor and applying the material to a backing. When hardened or cured, the material forms a film in which the particles or beads provide physical irregularities at the surface, resulting in a matte finish. Particles or beads must be blended homogenously in the coatable material, and further processing of the material (e.g., pumping, coating, filtering and drying) is required to provide a film with a suitable finish. Dispersing beads or particles uniformly in a coatable material and maintaining the homogeneity of the resulting blend is difficult. Point defects and streaking are often seen in the finished articles, and merely pumping the coatable material can require special equipment to minimize damage to the particles. Particle filled coatable materials can be prone to the formation of patterns, such as mottle, caused by the drying process. The resulting articles typically have undesirable optical properties. Films intended for use in optical applications must be formulated to match the index of refraction of the particles with that of the coatable material which, in turn, requires control of the particle size distribution. Undesired scattering of light within the finished film can be due to a mismatch of the index of refraction of the particles relative to the bulk of the coatable material.
It is desirable to provide novel systems and methods for the manufacture of films having matte finishes.